A
Crewed Mission to Mars...

Launching
the Mission:

When can vehicles be launched?

What method of propulsion will
we use?

What will the launch vehicles
carry?

How many launches will there
be?

The orbits of Earth and Mars provide us with a
15 year trajectory cycle which is divided into 7 launch windows. Basically,
about every 26 months a launch window presents itself and it is during
this time that any spacecraft traveling to Mars must be launched. The
Reference Mission begins with the first launch of Mars-crew support equipment
in the year 2007. In each of the launch windows it is assumed that 3 successful
launches are made to a common safe landing site where each mission will
add to previously established infrastructure.

1) Propulsion for Inbound Mars
Transit

Conventional chemical rockets (currently used
for the space shuttle) will be used to launch Mars-bound spacecraft into
LEO. The propulsion system that will most likely be used by the Mars transit
vehicles once in LEO will be Nuclear Thermal Propulsion. Developed to near-flight
status in the 1960s, for any given velocity change, a nuclear thermal rocket
(NTR) uses about half as much propellant as a chemical engine. The liquid
hydrogen NTR rocket will be used only after the spacecraft has left the
Earth's atmosphere and adequate shielding will exist in the trans-Mars
injection (TMI) stage of the transfer vehicle to protect the astronauts
from radiation which will develop while the rockets are firing. The NTR
will only be used on the outbound leg of the mission; the main benefit
being the increased payload capability of such a rocket due to the dramatic
reduction in required fuel for transit. Other theoretical and untested
methods of propulsion exist, but only NTR technology is both feasible and
significantly developed for use on a near-future mission.

2) Launch Schedule

The
following launch schedule is intended for reference use only; none of these
launches have approval or funding. Nonetheless, the sequence of launch
events seen here can be applied starting in any of the 7 launch opportunities
within any 15 year trajectory cycle.

A) The September 2007 Opportunity:

Launch 1 (Cargo) - A fully fueled Earth
return vehicle (ERV) is delivered to Mars orbit on the minimum energy trajectory.
The ERV will contain supplies for the crew on their return to Earth and
it will be identical to the habitat used by the astronauts during their
stay on, and their transit to, Mars. The ERV will also include an Earth
re-entry capsule in which the crew will "splash down" into the
ocean upon Earth return in much the same way as the astronauts of the Apollo
missions.

Launch 2 (Cargo) - This launch will send
mission critical equipment to the surface of Mars, also on the minimum
energy trajectory. The payload will consist of an unfueled Mars ascent
vehicle (MAV), a liquid oxygen/methane propellant production module, a
160 kW nuclear power module, a supply of liquid hydrogen (to be explained
later), a utility truck, and a pressurized rover.

Launch 3 (Cargo) - Here a surface laboratory,
a second 160 kW nuclear power module, a utility truck, tools, spare parts,
and a remotely controlled rover will be delivered to the Mars surface via
the minimum energy trajectory. The second nuclear power module will provide
complete power system redundancy and, should it become necessary to use
the laboratory module as an emergency shelter, the surface laboratory will
contain non-perishable food supplies for the crew.

B) The October 2009 Opportunity:

Prior to launching further cargo missions or the
crew, all surface equipment delivered during the 2007 launch window will
need to be checked out. It must be confirmed that the previously delivered
MAV is fully fueled and that all safety and mission critical systems check
out. The ERV in Mars orbit must also be verified to be fully functional.
If any of the crew safety or mission critical systems are not functioning
properly, the crew launch will be postponed until those systems can be
restored or replaced. System redundancy is crucial to the safety of the
Mars astronauts; especially the MAV and the ERV systems.

Launch 1 (Cargo) - This launch is identical
to the first launch of the 2007 opportunity. A second fully fueled ERV
is delivered to Mars orbit on the minimum energy trajectory. This ERV will
provide return vehicle redundancy for the first Mars crew and, if unused
by the first Mars crew, this ERV will be used by the second Mars crew due
to be launched in the window beginning late in 2011. Typically, the ERVs
will remain untended for 4 years before they are used by a returning Mars
crew.

Launch 2 (Cargo) - This launch will be
similar to the second launch of the 2007 opportunity. A second unfueled
MAV will be delivered along with a second liquid oxygen/methane propellant
production module, more liquid hydrogen, scientific equipment, spare parts,
and bioregenerative life support equipment. The second MAV provides system
redundancy for the Mars crew in the event that the first MAV is somehow
inoperable. The MAVs will generally be on the Mars surface for 4 years
before use due to the ascent vehicle redundancy necessary to ensure the
safe return of the astronauts. The bioregenerative life support equipment
is not critical to mission success, but it will be a valuable experiment
in life support system technology. It is hoped that a bioregenerative life
support system could be used to produce small amounts of fresh food and
also help to recycle air and water.

Launch 3 (First
Mars Crew) - This will be the first
crewed vehicle ever to make the journey to Mars. They will depart in mid-November
of 2009 on the fast transit trajectory. The 2009 window is the "worst
case" scenario in which the transit time to Mars will be about 180
days. By initiating the human Mars exploration program during the most
difficult transit scenario, we will be well prepared for all future missions.
The fast transit trajectory will put the astronauts in Mars orbit about
2 months before the arrival of the fourth and fifth cargo missions. If
for some reason the astronauts are unable to land at the site of the previous
cargo missions, the astronauts' transit module will contain all of the
crew provisions needed for the 180 day transit as well as the 500-600 day
surface stay (the arriving MAV could then be redirected to land nearby).
The transit module will also serve as the main crew quarters during the
astronauts' stay on Mars.

The first Mars crew will likely consist of 6 or
7 individuals who possess expertise in several disciplines. Some of the
areas of knowledge that will be required by the crew will include: 1) maintenance,
repair and operations of mechanical, electrical, and electronic devices
2) general medicine including surgery, psychology, and biomedicine 3) geology,
geophysics, paleontology, geochemistry, and atmospheric science 4) biology,
botany, ecology, and social science. In addition to these areas of expertise,
all crew members will require extensive skills in management, communications,
computer science, navigation, and journalism (a large part of the return
on mission investment is the reporting of surface operations to the population
of Earth).

C) The December 2011 Opportunity: &
D) The March 2014 Opportunity:

The next two launch windows will closely mirror
the 2009 launch opportunity. Each window will consist of two cargo launches
followed by one crewed vehicle. The equipment carried by the cargo missions
will depend upon several factors: 1) the suggestions made by the first
crew 2) required spare parts 3) status of surface systems (ie. system redundancy
must be maintained) 4) scientific objectives (these are likely to change
as the mission proceeds).

While they will be similar to the 2009 mission,
it would be impossible to predict the exact structure of the 2011 and 2014
Mars missions. Unforeseen developments on the Martian surface, as well as
developments here on Earth, will certainly alter the course of human Mars
exploration to some degree. One thing that is for certain is the fact that
the 2011 and 2014 missions will build on the infrastructure and scientific
achievements of the mission(s) before them. Over the course of the total
of 12 launches from Earth, significant amounts of equipment will accumulate
at the landing site and Mars surface operations experience will be continually
developed. Our expanding knowledge of Mars as a planet will lead us is
new directions of exploration, on Mars and on Earth, and perhaps a second
Mars landing site will be selected for future investigation. The experience
gained from previous Mars missions will streamline the process of "outpost"
establishment significantly and advances in technology will make Mars increasingly
accessible to astronauts. As old questions are answered and new ones are
raised, we will be well on our way to establishing a future in which we
step out into the stars in search of answers. As one can imagine, a human
Mars exploration program spanning only 9 years would certainly provide
significant returns.